Production of motor fuel



H. H. MEIER PRODUCTION 0F MOTOR FUEL Filed April 13, 1939- mzzmmow. uzsmom. 596mm /yAjoRNEYQ 5.50.... a nu Patented efe. 2, 194i ATET raonUcrroN or Moron FUEL Herbert H. Meier, Baytown, Tex., assigner to Standard Oil Development Company, a corporation of Delaware application April 13, 1939, serial No. 267,580

(ci. 19e-1o) 1o canna lower boiling hydrocarbons, suchk as. C4 and Cs hydrocarbons. Some of the'members of these groups are highly desirable constituents of motor fuel-s, particularly aviation gasoline because of their high octane number blending value and their vapor pressures. On the other hand, these fractions contain a number oi constituents which are undesirable because of their detrimental effect on the octane number of gasoline.

More specifically, isopentane and the various amylenes are desirable constituents in a iinished gasoline, While normal pentane is an undesirable constituent. Because of the presence of the various amylenes in the mixture, separation of the iscpentane from the normal pentane is impractical frorn an economic standpoint. Moreover,Y normal pentane cannot be removed from the mixture without removing certain amylenes the presence of which is desirable.

According to the present invention, the isopentane in such cracked products is made available and the normal pentane 'is made readily separable without sacrificing any of the amylenes by isolating the C5 fraction and alkylating it with isobutane or, if desired, with higher isoparamns. Isobutane is preferred for this purpose because it reacts with the amylenes in the presence of a suitable alkylation catalyst, such as sulfuric acid, aluminum chloride, BFs, and the like, to produce a product which is rich is isooctanes. This product usually contains the same or a lgreater amount of isopentane than the amount contained in the original C5 cut.

According to the present invention, the product obtained from the allrylation of the C5 fraction is readily fractionated into a C4 fraction which will be composed substantially-entirely of excess isobutane, which can be recycled to the alkylation unit, an isopentane fraction, which can be reblended with the original base stock, if lthe latter is suitable for aviation gasoline, or with a base stock selected for this purpose, a normal pentane' fraction, which can be utilized inmotor gasoline for fill, and a fraction ranging from Ce hydrocarbons' upwardly, which itself may be used as a base stock for aviation gasoline or can be blended with the same base stock to which the i-sopentane fraction is added. A separation` of the isopentane from the normal pentane is simplified by the method of the present invention by reason of the elimination of the amylenes which, in turn, are converted into highly desirable constituents for aviation gasoline.

In a specific embodiment of the present invention, cyclopentane is isolated for use as a blend# ing agent for octane number improvement. Cy-

clopentane, by reason of its boiling point, is readily separable` from the various hexanes, except 2 2-d1-methy1butane which oritseif, however, is

an isoparaiiln of high octane number blending value and, therefore, a desirable adulterant for the cyclopentane. Inthe practice of this embodiment, the initial C5 cut is cut high enough to include cyclopentane which isfed through the alkylation zone with the C5 out and the added isoparafiin, and is then recovered from the product after the recovery of normal pentane. In other words, the practice of this speciiic embodiment includes an additional fractionatlng step on the alleviation product.y

The present invention will be better understood from Va detailed description of the accompanying drawing in which the single iigu're is a. front elevation in diagrammatical form of a plant vsuitable for its practice.'

Referring to the drawing in detail, numeral i designates a fractionating tower to which is fed through vline 2 a cracked distillate or any other mixture of hydrocarbons containing Ca and lighter oleiins and lsoparaiiins. 'The tower is preferably so operated as to produce an overhead containing Ca and lighter hydrocarbons, a side stream containing C4 hydrocarbons, a second side stream containing C5 hydrocarbons, and bottoms containing Cs and heavier hydrocarbons. The overhead leaves the tower through line 8,- the C4 fraction leaves the tower through line' i, the C5 fraction leaves the tower through line 5, and the bottoms leavethe tower through line 6.

The mixture recovered through line 5 is fed to an alleviation zone 'l which, for expediency, is

represented by a simple rectangle, but which will be understood to be a conventional alkylation unit in which is circulated a mixture of alkylation catalyst, such as sulfuric acid of a. strength preferably in excess of/ alkylation product, and unreacted initial material, and from which isA continuously withdrawn a certain portion which isl separated into alkylationproduct. alkylation catalyst and unreacted initial material, the first being fed to a suitable refining and fractionating apparatus, and the second and third being returned to the circulating' stream. To

this alkylation zone through line 8 is also fed isobutane or other selected isoparaiiin.

The alkylation product is introduced into a debutanizing tower 9 which is maintained under pressure and temperature conditions such that unreacted isobutane is discharged from the 'top through line I and recycled to feed line 8, and stabilized product is discharged from the bottom through line Il into a fractionating tower I 2, which is maintained under suitable pressure and propr temperature to yield an overhead composed essentially of isopentane which leaves the tower through line 3.

The isopentane-free product is withdrawn from the bottom through line Il and discharged to awith and the normal pentane recovered from tower I2 as a side stream.

The pentane-free product leaves tower I5 through line II and is discharged into a further fractionating tower I8 which is so operated as to produce a Ca and lower fraction and a C9 and heavier fraction, the latter leaving the tower at the bottom through line I9 and the former leaving the top of the tower through line 20. Depending on the character of theaviation gasoline desired and the blending requirements, the overhead from tower I8 may be varied so as to include some of the Cn hydrocarbons.

As previously indicated, isopentane recovered from the system through line I3 and the Ca.- fraction recovered from the system through line 20 may, in some instances, be blended together to produce an aviation gasoline, or may both be blended with a suitable straight run base stock for this purpose. Also as previously indicated, when the initial C5 cut is so selected as to contain cyclopentane, this hydrocarbon may be recovered as a side stream from tower I5 or as an overhead from a tower interposed between tower I5 and I8. Itvmay be mentioned here also that in the initial fractionating tower I it is not necessary to recover a C4 fraction and a C5 fraction independently, because most of the advantages of the present method can be secured' by blending these fractions or recovering them in a single lstream and feeding them to the alkylation unit.

The conditions to be employed in the alkylation zone are well known, but may be recapitulated briey as follows:

The temperatureA selected may be any temperature below about 150 F. and is preferably room temperature or lower, excellent results having been obtainedat temperatures between about 20 and 70 F. and particularly at about 35 F. The operating pressure is made suilciently high to maintain the reactants in the liquid state at the temperature employed. Generally, a large excess of added isoparaihn to olen will be maintained in the reaction mixture by maintaining a high ratio of recycle stock to feed stock and by maintaining a ratio at least 2:1 and preferably at the order of 10:1 of added isoparain to olein in the feed stock. As is known, fresh make-up acid should be substituted periodically for a corresponding portion of the reaction acid so as to maintain acid strength at the desired level.

It will be understood that the present invention is not limited to the employment of any particular catalyst inthe alkylation zone or to the maintenance of any particular operating conditions in that zone or to any particular source of C5 hydrocarbons. What the invention is primarily concerned with is rendering available isopentane from a mixture of hydrocarbons containing it in combination with normal pentane and amylenes with the simultaneous conversion of the amylenes into desirable aviation gasoline constituents.

The nature and objects of the present invention having thus been described and illustrated, what is new and useful and is desired to be secured by Letters Patent is:

1. A method for recovering isopentane from a hydrocarbon mixture containing it in combination with normal pentane and amylenes which comprises reacting the mixture with an added isoparafiin other than isopentane in the presence of an alkylation catalyst, and recovering a fraction essentially composed of isopentane from the alkylation product.

2. A method for recovering isopentane from a hydrocarbon mixture containing it in combination with normal pentane and amylenes which comprises reacting the mixture with an added isoparain other than isopentane in the presence of sulfuric acid of a strength in excess of about at a temperature and for a time suitable for the alkylation 'of the added isoparafiln by the amylenes, and recovering from the product of this alkylation a fraction essentially composed of isopentane.

3. A method according to claim 1 in which the added isoparaflin is isobutane.

4. 'A method according to claim 2 in which the added isoparaiiln is isobutane.

5. A method for producing blending agents of high octane number from a hydrocarbon mixture containing isopentane, cyclopentane, normal pentane and amylenes which comprises reacting the mixture with added isobutane in the presence of an alkylation catalyst, and recovering from the alkylation product a fraction essentially composed of isopentane and a fraction essentially composed of cyclopentane,

6. A method for producing blending agents of high octane number from a hydrocarbon mixture containing isopentane, cyclopentane, normal pentane and amylenes which comprises reacting the mixture with added isobutane in the presence of concentrated sulfuric acid of a strength in excess of about 90% at a temperature and for a time suitable for the alkylation of the added isoparain by the amylenes, and recovering from the alkylation product so produced a fraction essentially composed of isopentane and a fraction essentially composed of cyclopentane,

7. A 'method for producing aviation gasoline which comprises reacting a mixture containing isopentane, normal pentane and amylenes with added isobutane in the presence of an alkylation catalyst to produce an alkylation product, separating from the alkylation product a fraction ssentially composed of isopentane, a fraction es sentially composed of normal pentane, and a fraction containing a large 'percentage of Ca hydrocarbons, and combining the first and third fractions.

8. A method for producing aviation gasoline i produced a fraction essentially composed of isopentane, afraction essentially composed. of normal pentane, and a fraction containing a large percentage of Cs hydrocarbons, and combining the rst and third fractions.

9. 'A method of segregating isopentane from a C5 fraction containing parafns and oleflns while producing a high octane number, saturated, branched chain hydrocarbon fraction containing substantial amounts of Ca constituents which 10 comprises reacting and alkylating a C5 hydrocarbon fraction containing isopentane, normal pentane and amylenes with added isobutane under alkylating conditions in the presence of. an alkylation catalyst, fractionating a Q5 parailnic fraction from the reacted mixture and separating isopentane therefrom.

10. A process as in claim 9 wherein unreacted isobutane is recovered from the reaction product and returned toA the alkylation reaction, and wherein a Ce-'Cs alkylate is recovered. HERBERT H. MEIER. 

